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      1 //
      2 //  ANTLRLookaheadStream.m
      3 //  ANTLR
      4 //
      5 //  Created by Ian Michell on 26/04/2010.
      6 // [The "BSD licence"]
      7 // Copyright (c) 2010 Ian Michell 2010 Alan Condit
      8 // All rights reserved.
      9 //
     10 // Redistribution and use in source and binary forms, with or without
     11 // modification, are permitted provided that the following conditions
     12 // are met:
     13 // 1. Redistributions of source code must retain the above copyright
     14 //    notice, this list of conditions and the following disclaimer.
     15 // 2. Redistributions in binary form must reproduce the above copyright
     16 //    notice, this list of conditions and the following disclaimer in the
     17 //    documentation and/or other materials provided with the distribution.
     18 // 3. The name of the author may not be used to endorse or promote products
     19 //    derived from this software without specific prior written permission.
     20 //
     21 // THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
     22 // IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     23 // OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
     24 // IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
     25 // INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
     26 // NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     27 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     28 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     29 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     30 // THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     31 
     32 #import "ANTLRLookaheadStream.h"
     33 #import "ANTLRError.h"
     34 #import "ANTLRRecognitionException.h"
     35 #import "ANTLRCommonToken.h"
     36 #import "ANTLRRuntimeException.h"
     37 
     38 @implementation ANTLRLookaheadStream
     39 
     40 @synthesize eof;
     41 @synthesize index;
     42 @synthesize eofElementIndex;
     43 @synthesize lastMarker;
     44 @synthesize markDepth;
     45 @synthesize prevElement;
     46 
     47 -(id) init
     48 {
     49 	self = [super init];
     50 	if ( self != nil ) {
     51         eof = [[ANTLRCommonToken eofToken] retain];
     52 		eofElementIndex = UNITIALIZED_EOF_ELEMENT_INDEX;
     53 		markDepth = 0;
     54         index = 0;
     55 	}
     56 	return self;
     57 }
     58 
     59 -(id) initWithEOF:(id)obj
     60 {
     61 	if ((self = [super init]) != nil) {
     62 		self.eof = obj;
     63         if ( self.eof ) [self.eof retain];
     64 	}
     65 	return self;
     66 }
     67 
     68 - (void) reset
     69 {
     70 	[super reset];
     71     index = 0;
     72     p = 0;
     73     prevElement = nil;
     74 	eofElementIndex = UNITIALIZED_EOF_ELEMENT_INDEX;
     75 }
     76 
     77 -(id) nextElement
     78 {
     79 //	[self doesNotRecognizeSelector:_cmd];
     80 	return nil;
     81 }
     82 
     83 - (id) remove
     84 {
     85     id obj = [self objectAtIndex:0];
     86     p++;
     87     // have we hit end of buffer and not backtracking?
     88     if ( p == [data count] && markDepth==0 ) {
     89         // if so, it's an opportunity to start filling at index 0 again
     90         [self clear]; // size goes to 0, but retains memory
     91     }
     92     [obj release];
     93     return obj;
     94 }
     95 
     96 -(void) consume
     97 {
     98 	[self sync:1];
     99 	prevElement = [self remove];
    100     index++;
    101 }
    102 
    103 -(void) sync:(NSInteger) need
    104 {
    105 	NSInteger n = (p + need - 1) - [data count] + 1;
    106 	if ( n > 0 ) {
    107 		[self fill:n];
    108 	}
    109 }
    110 
    111 -(void) fill:(NSInteger) n
    112 {
    113     id obj;
    114 	for (NSInteger i = 1; i <= n; i++) {
    115 		obj = [self nextElement];
    116 		if ( obj == eof ) {
    117 			[data addObject:self.eof];
    118 			eofElementIndex = [data count] - 1;
    119 		}
    120 		else {
    121 			[data addObject:obj];
    122 		}
    123 	}
    124 }
    125 
    126 -(NSUInteger) count
    127 {
    128 	@throw [NSException exceptionWithName:@"ANTLRUnsupportedOperationException" reason:@"Streams have no defined size" userInfo:nil];
    129 }
    130 
    131 -(id) LT:(NSInteger) k
    132 {
    133 	if (k == 0) {
    134 		return nil;
    135 	}
    136 	if (k < 0) {
    137 		return [self LB:-k];
    138 	}
    139 	if ((p + k - 1) >= eofElementIndex) {
    140 		return self.eof;
    141 	}
    142 	[self sync:k];
    143 	return [self objectAtIndex:(k - 1)];
    144 }
    145 
    146 -(id) LB:(NSInteger) k
    147 {
    148 	if (k == 1) {
    149 		return prevElement;
    150 	}
    151 	@throw [ANTLRNoSuchElementException newException:@"can't look backwards more than one token in this stream"];
    152 }
    153 
    154 -(id) getCurrentSymbol
    155 {
    156 	return [self LT:1];
    157 }
    158 
    159 -(NSInteger) mark
    160 {
    161 	markDepth++;
    162 	lastMarker = p;
    163 	return lastMarker;
    164 }
    165 
    166 -(void) release:(NSInteger) marker
    167 {
    168 	// no resources to release
    169 }
    170 
    171 -(void) rewind:(NSInteger) marker
    172 {
    173 	markDepth--;
    174 	[self seek:marker];
    175 //    if (marker == 0) [self reset];
    176 }
    177 
    178 -(void) rewind
    179 {
    180 	[self seek:lastMarker];
    181 //    if (lastMarker == 0) [self reset];
    182 }
    183 
    184 -(void) seek:(NSInteger) anIndex
    185 {
    186 	p = anIndex;
    187 }
    188 
    189 - (id) getEof
    190 {
    191     return eof;
    192 }
    193 
    194 - (void) setEof:(id) anID
    195 {
    196     eof = anID;
    197 }
    198 
    199 - (NSInteger) getEofElementIndex
    200 {
    201     return eofElementIndex;
    202 }
    203 
    204 - (void) setEofElementIndex:(NSInteger) anInt
    205 {
    206     eofElementIndex = anInt;
    207 }
    208 
    209 - (NSInteger) getLastMarker
    210 {
    211     return lastMarker;
    212 }
    213 
    214 - (void) setLastMarker:(NSInteger) anInt
    215 {
    216     lastMarker = anInt;
    217 }
    218 
    219 - (NSInteger) getMarkDepthlastMarker
    220 {
    221     return markDepth;
    222 }
    223 
    224 - (void) setMarkDepth:(NSInteger) anInt
    225 {
    226     markDepth = anInt;
    227 }
    228 
    229 @end
    230